Molded noncellular, microcellular, or cellular polyurethane and polyurea parts have found many applications in the automotive and building industries. Such molded parts are typically produced by the RIM process, or can be made be molded by pouring the liquid system into an open mold which is subsequently closed during the foaming reaction. The problem confronted in the RIM method and the open pour method lies in removing the part from the surface of the metal mold. Traditionally, an external mold release agent, such as a silicone-based liquid, is sprayed onto the mold surfaces every time a new part is to be molded. Various efforts are under way to provide for an internal mold release agent contained in the liquid system to reduce or eliminate the need for application of an external mold release agent to the mold surfaces. Examples of such internal mold release compositions are disclosed, for example, in U.S. Pat. Nos. 4,585,803 and 4,895,879, wherein a metal salt of a long chain carboxylic acid, such as zinc stearate is mixed into a polyol using a tertiary amine compatabilizer and preferably having a sterically hindered aromatic diamine chain extender to make a polyurethane or a polyurea molding which releases easily.
Some internal mold release compositions which have met with varying degrees of success are described in U.S. Pat. No. 4,396,729, wherein separate streams of an organic polyisocyanate and an amine terminated high molecular weight polyether, amine terminated chain extender, and a mold release agent, such as a siloxane, are combined in a mold; and, in like fashion, EP 445614 A2 describes reacting a carboxylic acid and a polyether polyol with a polyisocyanate in a closed mold.
Other patents, however, describe the manufacture of certain prepolymers as internal mold release agents. For example, U.S. Pat. Nos. 3,925,527; 4,201,847; 4,254,228; and 4,868,224 describe the reaction between an active hydrogen containing fatty acid ester having a high molecular weight of from 500 to 5,000 and an organic polyisocyanate to produce a prepolymer which is then reacted with a polyether polyol composition to produce a molded product having mold release properties. Prepolymers having mold release properties have also been described in U.S. Pat. Nos. 4,033,912 and 4,478,893, which disclose the reaction between an organic mono- or polyisocyanate and a polysiloxane to yield a mold releasing prepolymer which is then reacted with a polyol composition to produce a molded product which releases from the mold. In another patent describing the use of polysiloxanes, there is dispersed in an organic preferably polyol-modified diisocyanate a siloxane compound whose reactive groups are inhibited by a silicone dispersing or inhibiting agent.